Why has the talk-radio host Rush Limbaugh given such positive coverage, over such a sustained period, to Donald Trump? Some of his conservative listeners want answers. Consider a caller on Tuesday’s show. Ted Cruz is someone who has proven his conservative character over years, the caller said, whereas Trump is “an overnight thing.” He told the talk radio host, “I'm a character guy, which I believe that's who you are.” But the caller was beginning to have doubts about Limbaugh’s earnestness.